How to Validate a SaaS Idea Without Pitching

The Insight

Most founders try to validate ideas by pitching them. They tell potential customers about the product, ask if they would buy it, and read polite enthusiasm as signal. Marius Meiners flipped that completely. Before Peec AI had a single line of production code, he built a working prototype in V0 in a day and a half, showed it to potential customers, and asked them to sign a letter of intent. Eight signed. Antler wired a 100K seed check on those LOIs. The decision rule: pitching makes you the salesperson. An LOI makes the buyer the seller. Until someone is willing to put their name on a non-binding document saying they would pay if you built this, they do not actually want it.

How They Did It

1. Build a working prototype in 1-2 days, not a deck. Marius used V0 to vibe code the first Peec AI prototype in 1.5 days. He had not written code in four years. It did not have to ship. It had to be real enough that a customer could see what they would be buying.
2. Show it, do not pitch it. When Marius reached out, he did not ask "would this be useful?" He sent the prototype and asked customers to react. Pitches let people be polite. Prototypes force a real opinion.
3. Ask for an LOI, not a yes. After each demo, Marius sent a non-binding letter of intent through DocuSign. Marius described the bar: customers had to be "so interested that they would at least like go into DocuSign, they would read through the LOI, they would make sure it's actually non legally binding." That friction filtered out polite enthusiasts.
4. Track the conversion. Marius closed 8 LOIs from his target list. That number told him Peec AI had real demand. Antler wired 100K based on those signatures.

What Trips Up Founders

Confusing curiosity for commitment. Most founders email 50 prospects, get 10 "this is interesting" replies, and call it validation. Curiosity is free. Commitment costs something, even if it is only clicking through DocuSign.

Talking through the demo. Founders show the product and immediately explain it. The right move is to share the prototype, ask what the customer would use it for, and listen. The customer's framing tells you what they actually want.

Asking for the sale before commitment. "Would you pay $X for this?" gets a soft yes. "Would you sign an LOI saying you would pay if we built this?" forces a real answer. The LOI question is the filter.

When This Doesn't Work

LOIs work when buyers are mid-market or larger and willing to sign a document. It breaks down when you sell to consumers or very small businesses, where contracts feel like overkill. For B2C or SMB, the equivalent is a small upfront payment or a credit card pre-authorization. The principle is the same: until something that costs the buyer changes hands, you do not have validation.

The Question

Before you build anything, ask: would my target customer sign their name on a piece of paper saying they would pay if this existed? If the answer is no, you do not have a startup yet. You have an interesting idea. Show them a prototype. Send the LOI. You will know within weeks.